Directive sound transmission



Patented Aug. 28, 1928.

UNITED SATES MAIN E, A CORPORATION OF MAINE.

HARVEY c. mums, or ANACOSTIA, iirs'rmc'r or COLUMBIA, AND max mason, or

. cnrcaeo, 'rnnmors'assreuoas TO surnummn DIRECTIVE SOUND TRANSMISSION.

Original application filed June 25, 1919,. SerialNo. 806385;. Divided and this application filed February 26, 1926. SeriaLlTo. 90,849.

The present invention relates to directive sound transmission. The object of the invention'is to transmit sounds and particularly submarine sounds, in a definite de sired direction. This is accomplished by the employment of a plurality of sound transmitting sources which are disposed in a predetermined spaced relation and from whlch are sent out sounds having predetermined phase relations. 0

This application is a division of appllcation, Ser. No. 306,685%, patented July 19, 1927, No. 1,636,510.

In the drawings in which we have illustrated diagrammatically one form of apparatus in which the invention may be embodied, Figure 1 is a schematic diagram showing a plurality of sound transmitters and connections for exciting them to produce a desired phase relationship. Fig. 2 1s an elevation of one of the magnetophones employed as sound transmitters, and Fig. 3 is a sectional view of the magnetophones.-

Referring to the embodiment of the invention illustrated in the drawings, twelve sound transmitters are shown disposed in a straight line. For submarine sound work these transmitters are located under water, either at a shore station or on the side or the keel of a ship. Such sound transmitters are of course made waterproof. A convenient form of sound transmitter for this purpose is a magnetophone such as is shown in Figs. 2 and 3. This magnetophone comprises a watertight casing 13 having a soft iron diaphragm 14', the outer surface of which is exposed to the water. The diaphragm 14 is vibrated by means of a magnet 15 enclosed in the casing 13 and supplied with an alternating current of the desired frequency through insulated lead wires 16.

In the illustrated embodiment of the invention, magnetophones numberedl to 12, inclusive, are disposed so as to occupy a fixed position with relation to the shore in the case of a shore station or to the ship in case they are mounted on a ship. The direction in which the sound is transmitted is determined by suitably adjusting the phase relation between the several magnetophone's. The current for exciting the magnetophones is generated by an alternating current generator 20 having the desired audible frequency, preferably in the neighborhood 1000 cycles per second. The current from the generator 20 is distributed to the magnetophones through loaded lines, arranged similarly to the loaded lines of the electriccompensator employed by the Navy for directive sound reception. The wiring diaphragm of such a distributing system is shown schematically in Fig. 1. It consists of a plurality of loaded lines indicated by reference numerals 21,.22, 23, 24, 25, 26, 27, 28, 29,, 30 and 31. Each loaded line consists of inductances in series, shunted by capacities in paralleL- For convenience in construction,'the loaded lines are made up of a plurality of units, each unit comprisin an inductance 40 and capacity 41. The e fect of such a loaded line is to retard the electric current pulsations traveling over it. By introducing more ofthese loaded line units between the generator 20 and any 'one of the magnetophones, the phase of the current at such magnetophone is lagged betions A and B. The number of units of the sections A and B may be varied by the switching device, so that any desired number may be put in series with the lead 44 while the remaining sections are put in series with lead 45. The ends of the line21 are connected throu h leads 47 and 48 to the loaded hues 22 an 23, respectively, the ends of leads 47 and 48 bein' provided with contact points which ma e connections at any points along the loaded lines 22 and 23,

respectively. The current flowing through the lead 47 and entering the-loaded line 22 will divide, passing to the left and right along the sections of this line indicated by reference letters C and D, respectively. By moving the contact point 29 the number of units in the sections 0 and D may be varied SIGNAL COMPANY, OF I'QRTLAND,

as desired. Similarly the current is divided through loaded line 23, passing through the two sections of this line indicated by reference letters E and F, respectivel The end of section C of the loa ed line 22 is connected to lead 60 which has two branches, one terminating in a contact point 61 movablealong the loaded. line 24 and the other passing through the loaded line 28 to the magnetophones 2. v The loaded line 28 has one half of the retarding effect of the loaded line 24, so that when the contact point 61 is in the middle of the loaded line 24 the magnetophones -1, 2 and 3 are in phase with each other. They may be, however, thrown out of phase by moving the contact point 61 along the loaded line 24. The other end of the loaded line 22 is similarly connected to the magnetophones 4, 5 and 6 through the loaded lines 25 and 29. One end of the loaded line 23 is similarly connected to magnetophones 7, 8 and 9 through loaded lines 26 and 30, and the other end of the loaded line 23 is connected to the magnetophones 10, 11 and 12 through the loaded lines 27 and 31.

' Suitable contact switches 62, 63 and 64 are provided for the loaded lines 25 to 27 having the same operation as the contact switch 61 has on the loaded line 24. The several switches 46, 49, 54, 61, 62, 63 and 64 are connected together so as to be opera-ted in unison and to make contact in properly re lated pointsalon the loaded lines. The rotary switch employed by the Navy is suitable for this purpose. Such a switch is well known to those skilled in the hydrophone art and the structural details are not here specifically described. This type of r0- tary switch is illustrated and described in co-pending application of George W. Pierce for electric compensators, Serial No. 306,- 689 and the corresponding British Patent No. 146,193 of Oct. 25, 1921.

Instead of having the form of switch diagrammatically indicated at reference numeral 46 which interrupts the line 21, a form of switch like that shown on 49 or 50 may be employed which would simply make contact along the several units of the line 21 allowing the current to divide through the two sections A and B. It is preferable to use the type of switch indicated by reference numeral 46 which divides the loaded line 21 because by using this type of switch, the distributing system may be used as an electric compensator for the determination of the direction of a sound received by the magnetophones, which will operate as sound receivers as well as sound transmitters. The switch 42, is a double throw switch by means of which the two leads 44 and 45 may be connected to the two'receivers and 71 of a telephone head set, and the system may be used as a listening system giving both the binaural and maximum effect, as will be readily understood. by anyone skilled in the hydrophone art.

The electrical constants of the units in the several loaded lines and the number of units in each line are computed so that for any setting of the compensator switch, there will be the same phase dilference between the successive equally spaced transmitters. For example, When-the compensator switch is turned so that the several com onent switches make contact with the mid les of the several loading lines, the sounds generated at the several magnetophones will allbe in exact phase with each other. When, however, the compensator switch is turned from the middle connections along the loaded lines, for example, to the right as shown in Fig. 1, the electric impulses at the magnetophone 1 will have the same phase difference or lag behind the electric impulses at the magnetophone 2, as electric impulses at the magnetophone 2 have behind those at the magnetophone 3, and so on along the line of magnetophones.

In order to minimize, reflections at the junction points made at the switch contacts lndicated at 49, 54, 61, 62, 63 and 64, the loaded lines arecomput-ated so that the impedance of the section of one line is approximately equal to the impedance of the divided circuit through the loaded line which it feeds. For example, the impedance of section B of the line 21 should a proximate the impedance of the branc h circuits through the sections E and F of line 23. Similarl the impedance of the section F of the hne 23 should approximate the impedance of the three branch circuits through the loaded lines 27 and 31. This relation cannot be exactly realized, but should be approximated as far as possible. The value of the electrical constants of the several loaded lines and their units is computated by the same formulae as employed in computing the constants of electric compensator, such for example as developed and used by the Navy Department at the Naval Experimental Station, New London, Connecticut. These formulae are well known to those skilled in the hydrophone art and for the sake of brevity are not given here at length. They are set forth in detail in the co-pending application of George W. Pierce forv electrical compensation, Serial No. 306,- 689 The predetermined phase relation between the sound waves radiated from the several sound transmitters 1 to 12 inclusive produces a wave front having a maximum intensity in a definite direction. For example, if the sound waves generated at the transmitters are all in phase, the energy of the wave front will have a maximum for directions erpendicular to the line of transmitters an the energy will fall oil rapidly mitted atits maximum in a direction inclined to the perpendicular to the line of transmitters. This is indicated in Fig. 1, in which the electrical connections are shown so that there is a predetermined time lag between the waves sent out from the several transmitters counting left. In this case the wave front will have a general conical outline, the wave traveling in a direction inclined to the left as indicated in the drawing. By turning the compensator switch, the phase diiference between the sounds sent out from the several Q receivers may be varied at Wlll so as to vary in which thesound is to be sent out. The

compensator may be used as a receiving system by throwing switch 42 to the two receivers 70 and 71 of the telephone head set. The setting of the compensator will' in this case give the angular bearing of the sound received according to the well known operation of the electric compensator.

While we have shown our invention as embodied in an electrically operated sound generating system, the invention may be embodied in other sound generating systems.

devices having-their effective portions, fac- 111g in the same direction in the same plane or 1n parallel planes which conslsts 1n independently actuating such effective portions to produce impulsesoccurring at.diiferences in timedrelation varying between zero and the time required for sound to travel the distance between the ends of the series of devices.

I 2. The method of producing .'a directed sound wave from a series of stationary sound producers having their effective port1ons radiating 1n the same plane which confrom right to sists in supplying said sound producers from a common electrical source and in successively retarding the transmission of the energy supplied from the source to the sound producers in varying increments until a plane wave is radiated 1n the desired direction.

. 3. The method of producing a directed sound wave from a series of stationary sound producers having their effective portions radiating in the same plane which consists originally in supplying said sound producers with electric current of the same frequency and phase' relation but in varymg said phase relation in arithmetic progression between the sound producers successively from one end of the series to the other until the sound wave having the desired direction is produced.

4:. The method of producing a directed sound wave from a series of stationary sound producers having their eifective portions radiating in the same plane which consists originally in supplying said sound producers with electric current of the same frequency and phase relation, successively retarding in steps the current supplied to successive producers from one end of the series to the other until the sound wave having the desired direction is produced.

5. The method of producing a directed sound wave from a series of stationary sound producers having theireifective por- VVhile it is preferred to have the several tions radiating in the same plane, and havtransmitters excited from a common source, lng connected between'the producers and the they may be otherwise excited provided the supply source electrical compensating means desired phase relationship is obtained; and whlch cons sts in providing a common source while it isv preferred to have the several reof alternating current ofthe desired freceivers disposed in a straight line, they may quency, in dividing the current and introbe otherwise disposed as for example around ducing a time lag between the divided porthe circumference of a circle as disclosed in tions, and again introducing time lags and the co-pendin patent application of Harvey continuing similarly the same operation C. Hayes on Determination of wave energy until the current arriving at the sound prodirection, Ser. No. 322,222. ducers has such a relation as to produce It is to be understood therefore that the .a directed sound wave in the desired direcinvention is not limited to its preferred emtion.

bodiment, but may be otherwise embodied within the scope of the following claims. '.What we claim as our invention is 6. The method of producing sound beams in varying directions at the will of the operator from a series of stationary sound pro- 1. The method of producing sound beams ducers having their effective portions radiathaving different directlons from a series of 1ng 1n the same plane which conslsts in imstationary compressional wave producing posing time lags varymg 1n progressive relationship from one sound producer to another upon the current supplied from. a source and in varying said time lags in similar progressive relationship to produce a beam of sound in the desired direction.

7. The method of producing sound beams in varying directions at the will of the operator from a series of stationary sound roducers having their effective portions ra iat- 10 ing in the same plane which consists in in-.

tardation to vary progressivelythe phase 10 of thzucurrent supplied to successive producers whereby a sound beam may be produced in any direction. 7

HARVEY C. HAYES. MAX MASON. 

